APES Unit 8

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uses large amounts of fossil fuels, water, inorganic fertilizers, and pesticides to produce large quantities of monoculture crops or feedlot stock.

Traditional Subsistence Agriculture

uses mostly human labor and draft animals to produce only enough crops or livestock for a family. This uses organic fertilizer (manure) which negates the need for extensive irrigation, and natural pesticides.

Traditional Intensive agriculture

Increased use of human labor, draft animals, fertilizer, and irrigation to get a higher yield per area cultivated to produce enough food for the family as well as to sell as a cash crop.

GREEN REVOLUTION

started in the US in the 1950's (1st) and then in India and Indonesia in 1967 (2nd)

Advantages of GR

produce greater number of crops using a high-yield hybrid monoculture crop (wheat & corn for the 1st, and rice for the 2nd green revolution)

Disadvantages of GR

uses large amounts of fossil fuels, inorganic fertilizers, water for irrigation, and pesticides

2 or more crops are grown at the same time on the same plot (wheat that uses nitrogen and a legume that puts the nitrogen back into the soil. (This is NOT the same as strip cropping!)

Agroforestry (alley cropping)

where crops and trees are alternately planted together

Polyculture

a more complex form of intercropping in which many different plants maturing at various times are planted together. This is by far the best of the strategies - using less fertilizer & water (root systems capture water & nutrients more efficiently), covering the soil year round so there is less soil erosion, multiple habitats are created for natural predators so fewer pesticides are used, fewer herbicides due to the competitive nature of multiple crop plants, and less damage by weather due to a variety of crops.

Undernourished

consumption of 100-400 less calories than the average daily requirement.

lower life expectancy, greater susceptibility to disease, lower productivity & quality of life

GENETIC MODIFIED ORGANISMS (GMO)

altering the genes of a plant or animal by inserting an alien gene to produce a new desired trait. This is done through traditional methods of cross-breeding or the newer method of genetic splicing, specifically transgenic genetic engineering.

Steps in genetically modifying a plant

1.Identify and extract the gene with the desired trait 2.Then remove the portion of DNA that has desired trait 3.Remove the plasmid from the DNA of E. coli and insert your desired DNA into it 4.Return the plasmid to E. coli and then grow in tissue cultures to make copies 5.Transfer the plasmid to a carrier (like agrobacteirum) 6.The carrier inserts the foreigh DNA into the plant cell to yield the transgenic cell 7.Transfer the plasmid to the surface of a 'gene gun' which will then inject the DNA into the plant cell 8.The plant will now grow with the new trait inserted and expressed in the plant (like disease resistance)

Traditional cross-breeding disadvantages

slow process, taking many years to produce a commercially viable species

Genetic Engineering Advantages

Uses less pesticides, fertilizer, water & land, Increased production and lower cost of food, Boost immunity and develop built-in vaccines for livestock & poultry, Remove lactose, so that lactose-intolerant people can eat dairy products, Create drought resistant crops for semi-arid lands, Create salt tolerant crops for areas of salinization, Faster & cheaper to produce, Can create crops that are tastier, more nutritious and keep longer, Create crops that can be grown for growing medicines, Increase biodiversity on specific species due to greater # of DNA pieces.

Genetic Engineering Disadvantages

Non labeled products could produce allergic responses with inserted DNA, Contamination of other crops through pollen being blown by the wind, Loss of nutritional value, Deduction of the efficiency of anitbiotics, New viruses can evolve from mass production of genetically modified (GM) crops, Increased pest resistance to GM crops, Overall loss of biodiversity due to fewer organisms being developed for crops - only the few staples are being enhanced, The technology of the GM crops is not shared (Monsanto has a terminator gene that requires farmers to buy the seed every year instead of being able to plant some of the saved seeds), GM crops can affect other animals other than the target animals - i.e.monarch butterfly caterpillars are dying when their milkweed plants have been contaminated with the pollen from Bt corn. No assurance of public liability for farmers of GM crops.

How to increase food production for the future

1.Introduce new foods - i.e. the winged bean (a protein rich legume plant which all parts of the plant are totally edible), insects (containing 3-4 times the protein of beef, fish or eggs). 2.Polycultures of perennial plants, which don't need reseeding every year, don't require tilling the soil, reduce energy use, save water and reduce soil erosion and water pollution from eroded sediment. 3.Increased use of organic farming with crop rotation

Methods for using water more sustainably

Use efficient irrigation - drip irrigation, LEPA sprinklers, Center-pivot low pressure sprinklers, Use drought resistant crops like sorghum and Withdrawing water from an aquifer no faster than it is replenished.

Rangeland

semi-arid land that native grasses have adapted to. If too many cattle are feeding off this area then desertification will take place.

Feedlots

where animals are fattened for slaughter by feeding on grain grown on cropland or meal produced from fish or from other animal by-products.

More cropland is devoted to feed livestock where it could be used for crops for people if livestock were fed crop residues instead (wheat straw, rice straw, & corn stalks), More water is used for irrigating those crops and to wash away manure in feedlots, Increased water pollution (fecal coliform contamination and eutrophication) from animal waste storage systems and increased use of fertilizers.

huge nets hang 50 feet below the surface of the water and can be 34 miles long. This leads to overfishing of the desired species and traps many dolphins, porpoises and seals. There has been a ban on the use of drift-nets since 1992 by the UN but the compliance is voluntary so is rarely followed.

Aquaculture (fish farms)

where saltwater and fresh water fish and shellfish are raised like livestock in feedlots are.

Creating Sustainable Agriculture requires

Slowing population growth, Reducing poverty so that people can grow or buy enough food for better health, Converting to organic farming and polyculture.

3 Types of Soils

clay, silt, sand.

Clay

very small sized and flat, uber fine, has as high a porosity as Sand but has a much lower permeability

Silt

midsized, fine, smooth

Sand

largest of soil types, irregular shaped, gritty,

Soil Profile

the cross-section of soil showing the different soil horizons (layers).

a quick way to determine soil type in the field. It is based on the texture (gritty vs smooth & sticky) as well as the length of the ribbon that can be created. (Forming a long ribbon is a characteristic of clay)

Soil Triangle

used to quantitatively determine the soil type after one has found the % Sand and % Silt in testing. Where the two percentages cross designates a certain type of soil.

Porosity

the amount of pores spaces between soil particles. This is found by saturating a known volume of soil and then finding the percentage of water to volume of soil.

Permeability

the rate at which water moves through soil. This is found by timing how long it takes for a known volume of water to go through saturated soil.

Acid Soils

can be neutralized by adding lime.

Basic Soils

(like those of southwestern US) can be neutralized by adding sulfur (which is slowly converted into sulfuric acid by bacteria).

Salinization

the increase in salt concentration on the surface of the soil due to excess irrigation

land is left fallow (not planted) when there would be insufficient soil moisture as in an excessive drought.

Deep-Rooting Crops

will dry out the subsoil so that the salts won't be dissolved. Examples of deep-rooted crops are alfalfa, safflower, wild ryegrass, tall wheatgrass and sweet clover.

Salt-Tolerant Crops

forage crops (Bermuda grass, tall wheatgrass, fescue) are more tolerant of increased salt concentrations. Planting these areas for grazing or for food for grazers will utilize the area better than planting for human consumption crops.

Snow Management

deep snowdrifts cause for more percolation down to subsoil which increases salinity. Standing stubble will prevent drifts or deep-rooted perennials.

Surface Drainage

draining ponds in recharge areas The use of open trenches, buried pipes, grassed waterways and adequate culverts will prevent ponding of water in fields

Summerfallow

(where the soil is plowed & disced leaving very little vegetation at the surface) it is effective in weed control, it retains soil moisture, it gives short-term nutrients (from the previous crop) to the soil, and reduces the risk of residue-borne plant diseases. It also leaves the soil vulnerable to water and wind erosion.

Other benefits of summerfallow can be achieved by

stubble mulching, zero tillage, weed control, snow management.

Stubble mulching

leaving the stubble of the previous crop as a soil cover

Zero tillage

Replanting using no-till practices

Weed control

by using stubble, no-till, and/or cover crops

Snow management

decreasing the size of snow drifts by removing snow fences

To retain topsoil and reduce soil erosion from wind and water these conservation practices can be taken

1)Humus from organic aids in water retention (natural soil moisture), 2)Humus is bulkier providing more air spaces. Inorganic don't so there is more soil compaction. 3)Fewer air spaces in compacted soil = less O2 content = less absorption of I. fertilizer in soil 4)I. fertilizers only contain 2-3 of the 20 needed nutrients for plants. Manure contains almost all. 5)I. fertilizers cost more due to productions, transportation, and application 6)I. fertilizers cause more water pollution from excess applications 7)I. fertilizers release N2O (a greenhouse gas) 8)I. fertilizers contain high levels of NO3- which causes blue-baby syndrome.

Soil Erosion

3 types of erosion - sheet, rill, gully

Farming Methods

1)Traditional - 1830's, 2)Modern Intensive (Green Revolution and current time period), 3)Organic (Sustainable - uses the best of both)

Delaney Clause -Forbid the addition of any amount of known carcinogens to food and drugs, based on the assumption that any exposure represented unacceptable risks

FPCA

Federal Pesticide and Control Act -Required the registration of all pesticides

Toxic Substances Control Act

Authorized the EPA to ban or regulate chemicals deemed a risk to health or the environment

FIFRA

Federal Insecticide, Fungicide, and Rodenticide Act -Requires all commercial pesticides be approved by the EPA for general (over the counter) or restricted use (by trained professionals). The EPA is responsible for registering or licensing all pesticides. -Requires the EPA to test the pesticides and determine whether they cause any health risks (cancers, reproductive effects) .(After 25 years less than 10% have been tested due to lack of funding and manpower) -The EPA sets a tolerance level for the amount of residue that can remain on a crop when it gets to the grocery store (the levels are set for adults and not children)

FFDCA

Federal Food, Drug, and Cosmetic Act -Establishes the tolerances of pesticides for food and feed products. The FDA is responsible for administering this Act.

FQPA

Food Quality Protection Act (amended both FIFRA and FFDCA) -Requires new tougher standards for pesticide tolerance levels in foods based on a reasonable certainty of no harm to human health through dietary exposure and drinking water. (this replaced the Delaney Clause) -Requires manufacturers to demonstrate that active ingredients are safe for infants and children. -Allows the EPA to apply an additional 10-fold safety factor for children on dose amounts -Allows the EPA to consider exposure to more than one pesticide when setting pesticide tolerance levels

SDWA

Safe Drinking Water Act -To protect the quality of drinking water in the US for both underground and surface water. The EPA sets the standards for certain chemicals. -It requires a testing program for chemicals and pesticides for possible endocrine disrupting effects.

CERCLA

Comprehensive Environmental Response, Compensation and Liability Act -Created a "Superfund" for emergency response, spill prevention, and site remediation for toxic wastes. -Established the liability for clean up costs of the superfund sites

toxic to specific group of pests only. Example: soap is a selective pesticide because it will kill (through dessication) only soft-bodied insects leaving those with hard shells (carapace) like ladybugs alone

Pesticide benefits

1)Saves human lives - from such insect borne diseases such as malaria, bubonic plague, and sleeping sickness. 2)Increase food supplies and lower food costs - about 55% of potential food supply is lost to pests before (35%) or after (20%) harvest. 3)Increase profits for farmers - for every $1 spent on pesticides leads to an increase in US crop yields worth $4. 4)Work faster and better than alternatives - long shelf life, are easily shipped and applied, and safe when handled properly. 5)The health risks of pesticides are insignificant compared with their health benefits and other benefits. 6)Many new pesticides are used at very low rates per unit area compared to older products - approx. 100x lower than older ones

The IDEAL pesticide would

1)Kill ONLY the target pest. 2)Harm NO other species. 3)Break down into harmless compounds soon after being applied (days)-NO persistence. 4)Not cause genetic resistance in target pests. 5)Be inexpensive

Pesticide Problems

1)Genetic resistance by pests -within 5-10 years pests can develop immunity -they breed a lot! 2)Broad spectrum insecticides kill natural predators and parasites that may have been maintaining the pop of pest species. 3)Wiping out natural predators can also unleash new pests whose pop the predators had previously held in check - 100-300 secondary pests have been escalated to major pest status due to insecticides. 4)Some pesticides bioaccumulate leading to disastrous problems for higher organisms. 5)There is a correlation between human health disease and pesticides though no direct link (epidemiology). They produce a variety of health problems (cancers, nervous disorders, reproductive disorders) in both animals and humans

an organic compound containing chlorine. DDT is one. They are broad-spectrum insecticides. They are slow to degrade and so persist in the environment (in organisms as well as in nature) for years. Most have been banned since the advent of Rachel Carson's book, Silent Spring.

Organophosphates

organic compounds that contain phosphorus and were created from German nerve gas. Malathion is an example. They are more poisonous than other insecticides and they are toxic to other animals other than insects, especially humans. They do NOT persist in the environment as long as chlorinated hydrocarbons. They are used in large scale agriculture but are not available to the consumer because of the toxicity of them. Those who work with them in agriculture have to attend classes to learn how to use them and also protect themselves while spraying.

Carbamates

derived from carbamic acid. They are broad-spectrum insecticides and are not as toxic as organophosphates to humans though they do show broad, non-target toxicity. Sevin dust is an example.

Botanicals

derived from plants. These are more pest specific and easily degrade in the environment and have a low toxicity level. Nicotine, pyrethrum, and rotenone are examples. Botanicals are easily degraded by microorganisms and so do not persist in the environment.

Grass (herbicide)

only kill grasses but are safe most other plants

Selective (herbicide)

kill only specific vegetation 2,4-D and 2,4,5-T are examples

Broad-leaf (herbicide)

kills those plants with broad-leaves but not grasses. These are similar in structure to a natural growth hormone in plants and disrupt the plant's natural growth processes. In otherwords they will kill dandelions but not grasses. Wheat, corn, and rice are considered grasses so these herbicides can be used on weeds growing amongst the grains.

Agent Orange

(used in the Vietnam war to defoliate trees so the enemy could more easily be spotted) contained an combination of 2,4-D and 2,4,5-T plus a minute portion of dioxins (a chlorinated hydrocarbon). These dioxins cause birth defects in animals and humans as well have been associated with some cancers.

Pesticide treadmill

when farmer increase the amount of pesticide sprayed on their crops due to increased genetic resistance Greater amounts of pesticide have been shown to be ineffective in combating increased pest problems. More food is lost to pests today (37%) than in 1940 (31%) even though more 10x the pesticides are being used.

Bioaccumulation

the build up of pesticides through the food chain. Since the pesticide is stored in the fatty tissue of organisms it will be passed on when the organism is eaten, thus accumulating in each higher trophic level. The physical effects that arise from this is called biomagnification.

IPM - Integrated Pest Management

each crop and its pests are evaluated as parts of an ecological system. Then a control program is developed that includes a mix of cultivation and biological and chemical methods applied in proper sequence and with the proper timing. A well designed IPM program can reduce pesticide use and pest control costs by 50-90%. It can improve crop yields, reduce inputs of fertilizer and irrigation water, and slow the development of genetic resistance because pests are assaulted less often and with lower doses of pesticides. Widespread use of IPM is hindered by government subsidies of conventional chemical pesticides and by opposition from agricultural chemical companies.

Methods of controlling pests

1)Crop rotation 2)A barrier that surrounds the crop that provides a habitats for the pests natural enemies (ladybugs, spiders) 3)Biological control through natural predators of pests 4)Changing planting times so that pests either starve or are eaten by their natural enemies 5)Trap crops can be planted that lure pests away from the main crop 6)Light boxes (bug zappers), Bug bags 7)Practice intercropping, alley cropping, polyculture, polyvariety 8)Cultivate crops that are resistant to certain pest insects 9) Introduction of pesticides that are made from plants that can disrupt metabolism 10)Introduction of microbes (such as Bt - a bacillus) to disrupt metabolism in pests 11)Use of hormones to disrupt the growth or reproductive cycle of pests or sterilization of insects 12) Irradiation of food crops after harvesting 13)Monitor crops for infestations & then Only spray when & where necessary 14)Plant natural herbs that pests have a natural aversion to- cayenne, mint, bay leaves, basil, marigold, boric acid, diatomaceous earth 15)Spraying with botanicals or soap.

The FDA is charged with protecting consumers against impure, unsafe, and fraudulently labeled food other than in areas regulated by FSIS. They are also are responsible for periodically testing foods for pesticides.

U.S. Department of Agriculture's (USDA) Food Safety and Inspection Service (FSIS)

FSIS has the responsibility for ensuring that meat, poultry, and egg products are safe, wholesome, and accurately labeled.

USDA's Animal and Plant Health Inspection Service (APHIS)

APHIS' primary role in the U.S. food safety network of agencies is to protect against plant and animal pests and diseases.

Environmental Protection Agency (EPA)

EPA's mission includes protecting public health and the environment from risks posed by pesticides and promoting safer means of pest management.

3 agencies oversee the regulating of pesticides in different areas

EPA, FDA, and the USDA

POPs (Persistent Organic Pollutants)

man made chemicals that do NOT break down in the environment over a long period of time (years) and also bioaccumulates throughout the food web

POPs fall into 3 broad categories

1)pesticides (primarily insecticides) 2)industrial chemicals 3)by-products & contaminants ** Lead, Cadmium, and Mercury are usually included in the group, not because they are organic (they are NOT - they are metals) but because they persist and bioaccumulate and have serious health effects

The grasses of the Midwest (Kansas, Oklahoma, Colorado, New Mexico) that had a complex root system were replaced by monoculture crops with simple root systems. Added to this change was the common practice of plowing the field after the harvest, leaving the soil exposed to strong winds during the winter months. The farming practices were changed with the Soil Erosion Act of 1935 that lead to the Soil Conservation Service (now named Natural Resources Conservation Service as part of the USDA). It promoted conservation practices such as contour plowing, crop rotation, conservation plowing, terracing, and windbreaks.

1)High yield from crops 2)Increased food reserves for world 3)Enhanced learning and effectiveness of GM crops

Cons of the GR

1)High cost of equipment 2)Excessive use of water 3)Increased salinization 4)Excessive use of inorganic fertilizers 5)Compaction of soil due to lack of humus 6)Less natural resistance to pests with hybrid GM crops 7)Excessive use of pesticides 8)Increased pest resistance to pesticides

planting alternating strips of one crop with another crop (i.e. corn with legume) The second crop (legume) traps the eroding soil from the first crop (corn) as well as trapping water and also providing a barrier to pests.

Alley cropping (agroforestry)

several crops are planted together in strips or alleys between trees and shrubs that provide fruit or fuelwood. The trees provide shade which reduces evaporation of precious water so that soil moisture is retained as well as providing fruit or fuel (if only dead limbs are cut).

Shelterbelts

a wider area than a windbreak that contains trees as well as shrubs to help reduce wind erosion, retain soil moisture, provide habitats for wildlife and fuel.

Gully reclamation

restoring severely eroded land by planting shrubs, vines, & trees to stabilize the soil, channels to divert fast moving water, and check dams that will fill up with silt and gradually fill in the gullies.

Cover crops

grasses or legumes that are planted at the end of a harvest so that the soil is not left exposed during the none growing season. These 'crops' can either be harvested for animal fodder or plowed under to help fertilize the soil before the next growing season.

Green Manure

legumes are planted and then plowed under to put nitrogen back into the soil.

doesn't add humus to soil so soil is drier, needing more irrigation; lowering oxygen content of soil which reduces the efficiency of nutrient uptake; releases nitrous oxide (N2O) which enhances global warming; requires a great deal of energy to produce and apply (the cost of equipment!) than organic fertilizer.

Methods to Increase Soil Fertility

1)Manure 2)Green manure 3)Compost 4)Mycorrhizae fungi that are found in the spores attached to the roots of plants (help in disease resistance & nutrient uptake).

Strip cropping, Alley cropping, Bio-pesticides (i.e. soap), Biological pest control, Light boxes, Polyculture, Insect birth control and/or hormones, GM resistant crops, Pheremones to attract pests (i.e. Japanese Beetle traps), Hot water, Spraying only when and where a pest outbreak occurs, Crop rotation, A barrier hedge that surrounds the crop that provides a habitat for the pest's natural enemies, Changing planting times so that pests either starve or are eaten by their natural predators, Trap crops that can lure pests away from the main crop, Introduce microbes (like Bt thurengensis) to disrupt the metabolism of pests, Use of IPM.

ecological definition of soil

a mixture of mineral particles, organic matter, water and air that is capable of supporting plant life.

Physical Weathering

the breakdown of rock (the regolith) into finer particles through weathering.

Chemical Weathering

the breakdown and redeposition of organic and inorganic substances primarily through the processes of oxidation, dissolving, and leaching.

Decomposition

the breakdown of organic matter by bacteria and fungi into simpler organic substances (carbohydrates, lignins, proteins)

Any food or element an organism must take in to live, grow, or reproduce.

organic farming

Producing crops and livestock naturally by using organic fertilizer (manure, legumes, compost) and natural pest control (bugs that eat harmful bugs, plants that repel bugs, and environmental controls such as crop rotation) instead of using commercial inorganic fertilizers and synthetic pesticides and herbicides. See sustainable agriculture.

organic fertilizer

Organic material such as animal manure, green manure, and compost, applied to cropland as a source of plant nutrients. Compare commercial inorganic fertilizer.

overgrazing

Destruction of vegetation when too many grazing animals feed too long and exceed the carrying capacity of a rangeland or pasture area.

overnutrition

Diet so high in calories, saturated (animal) fats, salt, sugar, and processed foods and so low in vegetables and fruits that the consumer runs high risks of diabetes, hypertension, heart disease, and other health hazards. Compare malnutrition, undernutrition.

pasture

Managed grassland or enclosed meadow that usually is planted with domesticated grasses or other forage to be grazed by livestock. Compare feedlot, rangeland.

perennial

Plant that can live for more than 2 years. Compare annual.

plantation agriculture

Growing specialized crops such as bananas, coffee, and cacao in tropical developing countries, primarily for sale to developed countries.

polyculture

Complex form of intercropping in which a large number of different plants maturing at different times are planted together. See also intercropping. Compare monoculture, polyvarietal cultivation.

polyvarietal cultivation

Planting a plot of land with several varieties of the same crop. Compare intercropping, monoculture, polyculture.

rangeland

Land that supplies forage or vegetation (grasses, grasslike plants, and shrubs) for grazing and browsing animals and is not intensively managed. Compare feedlot, pasture.

riparian zones

Thin strips and patches of vegetation that surround streams. They are very important habitats and resources for wildlife.

salinization

Accumulation of salts in soil that can eventually make the soil unable to support plant growth.

shelterbelt

See windbreak.

soil conservation

Methods used to reduce soil erosion, prevent depletion of soil nutrients, and restore nutrients already lost by erosion, leaching, and excessive crop harvesting.

soil erosion

Movement of soil components, especially topsoil, from one place to another, usually by wind, flowing water, or both. This natural process can be greatly accelerated by human activities that remove vegetation from soil.

strip cropping

Planting regular crops and close-growing plants, such as hay or nitrogen-fixing legumes, in alternating rows or bands to help reduce depletion of soil nutrients.

subsistence farming

Supplementing solar energy with energy from human labor and draft animals to produce enough food to feed oneself and family members; in good years enough food may be left over to sell or put aside for hard times. Compare industrialized agriculture.

surface runoff

Water flowing off the land into bodies of surface water. See reliable runoff.

sustainable agriculture

Method of growing crops and raising livestock based on organic fertilizers, soil conservation, water conservation, biological pest control, and minimal use of nonrenewable fossil-fuel energy.

terracing

Planting crops on a long, steep slope that has been converted into a series of broad, nearly level terraces with short vertical drops from one to another that run along the contour of the land to retain water and reduce soil erosion.

traditional intensive agriculture

Producing enough food for a farm family's survival and perhaps a surplus that can be sold. This type of agriculture uses higher inputs of labor, fertilizer, and water than traditional subsistence agriculture. See traditional subsistence agriculture. Compare industrialized agriculture.

traditional subsistence agriculture

Production of enough crops or livestock for a farm family's survival and, in good years, a surplus to sell or put aside for hard times. Compare industrialized agriculture, traditional intensive agriculture.

undergrazing

Reduction of the net primary productivity of grassland vegetation and grass cover from absence of grazing for long periods (at least 5 years). Compare overgrazing.

Horizontal zones that make up a particular mature soil. Each horizon has a distinct texture and composition that vary with different types of soils.

soil permeability

Rate at which water and air move from upper to lower soil layers.

soil profile

Cross-sectional view of the horizons in a soil. See soil horizon.

soil structure

How the particles that make up a soil are organized and clumped together. See also soil permeability, soil texture.

soil texture

Relative amounts of the different types and sizes of mineral particles in a sample of soil.

salinity

Amount of various salts dissolved in a given volume of water.

porosity

Percentage of space in rock or soil occupied by voids, whether the voids are isolated or connected

permeability

The degree to which underground rock and soil pores are interconnected and thus a measure of the degree to which water can flow freely from one pore to another.

leaching

Process in which various chemicals in upper layers of soil are dissolved and carried to lower layers and, in some cases, to groundwater.

biological pest control

Control of pest populations by natural predators, parasites, or disease-causing bacteria and viruses (pathogens).

chlorinated hydrocarbon

Organic compound made up of atoms of carbon, hydrogen, and chlorine. Examples are DDT and PCBs.

DDT

Dichlorodiphenyltrichloroethane, a chlorinated hydrocarbon that has been widely used as an insecticide but is now banned in some countries.

fungicide

Chemical that kills fungi.

herbicide

Chemical that kills a plant or inhibits its growth.

insecticide

Chemical that kills insects.

integrated pest management (IPM)

Combined use of biological, chemical, and cultivation methods in proper sequence and timing to keep the size of a pest population below the size that causes economically unacceptable loss of a crop or livestock animal.

pest

Unwanted organism that directly or indirectly interferes with human activities.

pesticide

Any chemical designed to kill or inhibit the growth of an organism that people consider undesirable. See fungicide, herbicide, insecticide.

polychlorinated biphenyls (PCBs)

Group of 209 different toxic, oily, synthetic chlorinated hydrocarbon compounds that can be biologically amplified in food chains and webs.